Introduction

Each drafting operation introduces fresh irregularity, the irregularity of the final yarn being the summation of irregularities produced during each operation. Roll drafting or the attenuation of slivers and Rovings to produce yarn of specified count is the most important principle involved in the processing of raw material into yarn. The irregularity introduced in drafting mainly depends upon the parameters of the drafting system, mechanical faults and quality of the input material. When mechanical faults are eliminated, drafting irregularities depend upon to control on the floating fibers in the drafting zone. Setting between the roller nips, distance between the apron at the nip, distance between the apron at the nip, and pressure on the top rollers are some of the factors. The characteristics of the sliver fed to the drafting system also exercise considerable influence on the irregularities introduced and drafting system operated under the optimum conditions. Short fiber content, neps, trash and other impurities degree of fiber parallelization and number and extend of residual hooks in the fibers together with their direction of presentation are some of the important factors that characterize sliver quality and determine its behavior during drafting.

Nutter and slater examined the effect of hooked fibers on yarn strength and found that better strength is obtained when a fiber tip is presented to the drafting system than a hooked end. Grade, Wakanker and Bhaduri found better yarn regularity and strength when majority hooks are fed as trailing then as leading to the ring frame. They further found that the yarn quality diminishes with increase in the number of majority hooks when these are fed as leading. Simpson, Deluca and Flori also confirmed that feeding majority hooks as leading to the ring frame contributed to poorer yarn quality and more breakages, the effect being pronounced in case of fine yarns. Apart from hooks, the fiber parallelization may also effect on drafting irregularities.

The treatment given to raw material during spinning process through various machines greatly influences not only the quality of spun yarn but also its quantum. Factors like setting between rollers, draft distribution, Pressure on top rollers, shore hardness of rubber cots, spacers, type/size of ring travelers, rings, relative humidity in the plant and mixing of raw material etc, contribute towards the quality and quantity of yarn. Moisture content in the raw material especially in cotton is very important because of its direct effect on yarn strength as well as elongation and neps in the yarn. Whereas the strength and elongation directly affect the performance of yarn in warping, the neps influence surface of finished cloth and dye take up.

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About the Author

The author is specialized in Compact Spinning, having 2 decades of rich experience in reputable groups and mills. He is also the writer of a book on "Statistical quality control".